AOL arguably has the best video search technology through their acquisition of Truveo in early 2006. Google also has a growing video search engine that includes both Google Video and YouTube videos.

Since many videos posted on the internet contain little or no associated meta data to describe what’s in the video, services like AOL’s Truveo and CastTV look at surrounding text to help determine what the video is about, and make it more searchable. Truveo does a great job with this. CastTV is much better based on the demos I’ve seen. Alex and Edwin won’t disclose all of the technology behind the service, but part of the trick is that they are able to track videos through multiple links on a site, collecting metadata along the way. And they also parse the code on the video files as well, gathering additional information about the content. If tags are available for the videos (such as YouTube tags), these are indexed as well. The final step is actually even more interesting – CastTV will take the data they are able to collect about a video and search the web in general for additional data. If there’s a close enough match, CastTV adds that information to the content metadata. And unlike other video search tools, CastTV indexes movies and shows from iTunes and other for-pay services.

The company says they will enter private beta next month; full launch will come this summer.